Mould and a method for forming an orthopaedic spacer made of medical cement

ABSTRACT

The modular mould ( 1 ) for forming an orthopaedic spacer made of medical cement defines a moulding cavity ( 2 ) delimited by a moulding surface ( 3 ) configured for impressing a predetermined shape on the medical cement and realising the orthopaedic spacer. 
     The mould ( 1 ) comprises a first sector ( 7   a ), defining at least a first portion ( 8 ) of the surface ( 3 ), and a second sector ( 7   b ) defining at least a second portion ( 12 ) of the surface ( 3 ). 
     The mould ( 1 ) comprises at least a first forming insert ( 14 ) insertable in a housing ( 13 ) fashioned in at least one of said sectors ( 7   a   , 7   b ) and comprises a respective portion ( 8, 12 ) of the surface ( 3 ), said respective portion ( 8, 12 ) of the surface ( 3 ) having an elongate shape which is configured for forming an elongate portion of said orthopaedic spacer.

The present invention relates to a mould and a method for forming a temporary orthopaedic spacer.

As is known, orthopaedic spacers are made of medical bone cement and have the purpose of temporarily replacing fixed prostheses up to a conclusion of treatment for septic infections, or like issues.

A prior art method for realising orthopaedic spacers includes modelling the starting bone cement directly in the operation theatre, so as to give the cement the predetermined shape.

In detail, with this method forming moulds are often used that comprise two moulding shells that are couplable to one another so as to realise a volume to be filled with the cement.

The shells can have shapes for realising a spacer that can be adapted to the shoulder, knee or hip joints, and others besides.

The known moulds disadvantageously enable only a partial flexibility of use.

In fact, the patients, as is well-known, have very different physiques and naturally require prostheses and spacers having dimensions corresponding to those of the limbs they will be used for.

Therefore, at present, either the surgeon uses a multiplicity of moulds for treating patients having different physiques or can treat only patients having those specific physiques which can be adapted to moulds placed on the market by manufacturers.

An aim of the present invention is therefore to make available a mould and a method for forming a temporary orthopaedic spacer which enable obviating the drawbacks of the prior art.

In particular, an aim of the present invention is to provide a unitary modular mould which enables realising orthopaedic spacers different for patients having different physiques.

The stated technical task and specified aims are attained by a mould and a method for forming a temporary orthopaedic spacer according to the appended claims.

Further characteristics and advantages of the present invention will become more apparent from the indicative, and hence non-limiting, description of the mould and the method of the invention.

This description will be set out below with reference to the attached drawings, provided solely for indicative and therefore non-limiting purposes, in which:

FIG. 1 is a schematic representation of the mould of the present invention;

FIG. 2 is a view from above of a first component of the mould of the present invention;

FIG. 3 is a schematic representation of a second component of the mould of the present invention;

FIG. 4 is a schematic representation of a third component of the mould of the present invention;

With reference to the accompanying figures, reference number 1 indicates a forming mould of an orthopaedic spacer made of medical cement, in accordance with the present invention.

The invention can also be used with known medical cements, which are however not described in detail in the following.

The mould 1 defines a moulding cavity 2 delimited by a moulding surface 3. The surface 3 is configured to impart a predetermined shape on the medical cement and to create an orthopaedic spacer.

In the embodiment illustrated in FIG. 1, the mould 1 comprises a first moulding element 4 a and a second moulding element 4 b.

The first moulding element 4 a comprises a first moulding surface 5 a and the second element 4 b comprises a second moulding surface 5 b.

In particular, the first element 4 a and the second element 4 b are configured for being superposed on one another, at an open lateral surface which comprises the first surface 5 a (in the case of the first element 4 a) and the second surface 5 b (in the case of the second element 4 b).

In still greater detail, the two moulding elements 4 a, 4 b can be specular and therefore symmetrical with respect to a join plane, at which they contact to define the closed mould.

The first element 4 a and the second element 4 b together define a containing volume of the medical cement and further components able to form the spacer, which will be described in the following.

In the closed configuration of the mould 1, a passage hole 6 is defined that is shaped by a first channel 6 a of the first element 4 a and by a second channel 6 b of the second element 4 b (see for example FIG. 1).

The passage hole 6 enables inserting medical cement in liquid state into the mould 1.

The first moulding element 4 a and/or the second moulding element 4 b are preferably made of polypropylene or of a polypropylene based material.

Since, in the preferred embodiment of the invention, the first and the second element 4 a, 4 b are substantially specular, for simplicity of description, in the following a detailed description will be made of only the first element 4 a, and what is described is also valid for the second element 4 b.

The first element 4 a comprises a first sector 7 a and a second sector 7 b defining the moulding surface 3.

The first sector 7 a, defines at least a first portion 8 of the moulding surface 3 and is for forming a first part of the orthopaedic spacer.

The mould preferably comprises a second forming insert 9 (illustrated in FIG. 3) suitable for inserting in the moulding cavity 2 of the mould 1.

In particular, the second forming insert 9 is insertable between the first portion 8 of the first moulding surface 5 a of the first element 4 a and the first portion 8 of the second moulding surface 5 b of the second element 4 b.

For the sake of precision, the second forming insert 9 has a complementary shape to a head portion 8 a of the first portion 8.

In greater detail, the second forming insert 9 is configured for shaping the “head” of the spacer, i.e. the rounded part of the conformation destined to take the place of the missing epiphysis of the bone.

The second forming insert 9 preferably comprises positioning means 10 configured for enabling the correct insertion of the forming insert 9 in the first portion 8 of the first surface 5 a (and/or the second surface 5 b).

The positioning means 10 comprises at least a pair of ribs 11 in relief on an external surface of the second forming insert 9. In particular, the ribs 11 are suitable for being operatively inserted into respective profiled portions 11 a of the first moulding element 4 a and/or the second moulding element 4 b.

In still greater detail, the second forming insert 9 has a forming surface shaped as a concave spherical cap shape 11 b, so as to be able to impress, on the bone cement, the form of the head of the spacer.

Preferably, the second forming insert is made of a TPE-SEBS based material; this is however not a unique solution.

The second sector 7 b defines a second portion 12 of the surface 3 and is for forming a second part of the orthopaedic spacer, adjacent to the first part.

In particular, the second sector 7 b comprises a housing 13 in which at least a half-part 14 a (illustrated in FIG. 4) is insertable, of at least a first forming insert 14 of the mould 1 (with reference to the second element 4 b, reference will be made to the half-part 14 b represented in FIG. 1 and complementary to the half-part 14 a).

The half-part 14 a comprises the second portion 12 of the surface 3 and has an elongate shape along a prevalent development direction configured for forming an elongate portion of the orthopaedic spacer in the superposed configuration of the first 4 a and the second element 4 b (and therefore in a superposed configuration of the half-part 14 a and the half-part 14 b, thus going to form the first forming insert 14).

The first forming insert 14 is preferably configured for forming a portion of rod or “stalk” of the orthopaedic spacer, i.e. the part having an elongate shape which is destined to couple with the residual diaphysis of the bone.

The second portion 12 of the surface 3 preferably has a tapered shape along the development direction in a distancing direction from the first portion 8.

Further, the second portion 12 of the surface 3 has a cone shape.

The mould 1 preferably comprises a plurality of first forming inserts 14 that are inter-replaceable, on the basis of the dimension of the spacer that is to be obtained.

In particular, each first forming insert 14 has a different width and/or length of the second portion 12, i.e. of the concave part, so as to realise orthopaedic spacers having different dimensions.

In practice, on the basis of the physical characteristics of the patient, spacers can be obtained having different transversal and/or longitudinal dimensions.

In the embodiment of FIG. 4, the second portion 12 of the surface 3 has the rod portion 12 a and a conduit 12 b configured for enabling insertion and distribution of the medical cement.

The first forming insert 14 is preferably made of a TPE-SEBS based material; this is however not a unique solution, as the first insert could also be made of polypropylene or another material besides.

As concerns the transversal dimensions of the spacer, the invention provides a good degree of modularity, as by replacing the first insert 14, spacers of different thickness can be obtained.

As concerns the longitudinal dimension, the invention enables a continuous modularity, as the length of the stalk or rod of the spacer is a direction function of the quantity of bone cement poured into the mould during the forming operations.

In fact, during the filling of the mould 1 with bone cement, the mould 1 is positioned so as to have the first portion 8 thereof inferiorly located with respect to the second portion 12, so that the passage hole 6 enables easy insertion of a portion of bone cement.

In this way, it is possible to regulate, with absolute precision, the longitudinal dimensions of the second portion 12 on the basis of the volume of cement inserted through the hole 6.

The mould further comprises a reinforcing element 15, possibly of known type, insertable in the two forming inserts.

The reinforcing element 15 is preferably made of steel and is constituted by a profiled plate 15 a, defined by a first portion 15 b and a second portion 15 c that are angled with respect to one another.

In this way, during the filling step of the mould 1 with the bone cement, the reinforcing element 15 is sunken into the cement, with the first portion 15 b remaining sunken in the head of the spacer, while the second portion 15 b is incorporated in the stalk.

The mould 1 comprises coupling means 17 configured for joining the first element 4 a and the second element 4 b in a superposed configuration of the first element 4 a with the second element 4 b. The coupling means 17 is conformed so as to join the first element 4 a and the second element 4 b by locking and/or jointing in order to position them correctly one on the other.

Once loaded with the medical cement (in the quantity necessary for obtaining the desired longitudinal dimensions), the mould 1 is pressed by a press of known type that is therefore not a part of the present description.

Once the cement has hardened, it defines the spacer with can therefore be removed from the mould and inserted in the patient's body.

The present invention relates to a method for forming an orthopaedic spacer.

The method includes predisposing a mould 1 realised according to the invention.

Therefore, the first forming insert 14 and the second forming insert 9 are selected on the basis of the characteristics of the patient's physique, i.e.

on the basis of the dimensions of the portions of bone on which the spacer intervenes.

A reinforcing element 15 is also predisposed, to be located internally of the two forming inserts, the dimensions of which element 15 are also a function of the physical characteristics of the patient.

At this point, the mould 1 is positioned so that the head portion 8 a is located inferiorly of the rod portion 12 a and the mould 1 is filled with bone cement, sliding the bone cement through the passage hole 6. The quantity of cement inserted defines the longitudinal dimensions of the spacer.

The pressing step of the mould 1 then follows, and the consequent solidifying step of the bone cement, so as to obtained the desired spacer.

The mould 1 and the method described in the foregoing are able to obviate the drawbacks that have emerged in the prior art.

The above-mentioned mould 1 advantageously enables obtaining an orthopaedic spacer that is specific for a specific patient by modelling the head portion 8 a by means of a second forming insert 9 and regulating the longitudinal and transversal dimensions of the rod portion 12 a by means of the first forming insert 14.

Still more advantageously, the first forming insert 14 enables both obtaining a plurality of transversal dimensions that are different from the rod or “stalk” of the spacer, simply by replacing the first forming insert 14 with another forming insert 14, and obtaining any longitudinal dimension of the rod portion, in the above-explained ways. 

1. A modular mould (1) for forming an orthopaedic spacer made of medical cement defining a moulding cavity (2) delimited by a moulding surface (3) configured for impressing a predetermined shape on said medical cement and for realising said orthopaedic spacer, said mould (1) comprising a first sector (7 a), defining at least a first portion (8) of said surface (3), and a second sector (7 b) defining at least a second portion (12) of said surface (3), wherein said mould (1) comprises at least a first forming insert (14) insertable in a housing (13) fashioned in at least one of said sectors (7 a, 7 b) and comprising a respective portion (8, 12) of said surface (3), said respective portion (8, 12) of the surface (3) having an elongate shape which is configured for forming an elongate portion of said orthopaedic spacer.
 2. . The mould (1) according to claim 1, comprising a first moulding element (4 a) and a second moulding element (4 b) respectively comprising a first moulding surface (5 a) and a second moulding surface (5 b), each moulding surface (5 a, 5 b) comprising said first (8) and second portion (12), and wherein said first forming insert (14) comprises two complementary half-parts (14 a, 14 b), each being insertable in a respective housing (13) of a respective moulding element (4 a, 4 b).
 3. The mould (1) according to claim 1, wherein said respective portion (8, 12) of the surface (3) defined by said first forming insert (14) has a tapered shape.
 4. The mould (1) according to claim 1, comprising a reinforcing element (15) insertable in said first portion (8) and said second portion (12) of the surface (3).
 5. The mould (1) according to claim 1, wherein said first forming insert (14) is insertable in a housing (13) of the second sector (7 b) and wherein the mould (1) further comprises a second forming insert (9) insertable in a respective housing of the first sector (7 a) and preferably having a forming surface shaped as a concave spherical cap shape (11 b) configured for impressing a respective convex spherical cap shape on a portion of medical cement.
 6. The mould (1) according to claim 2, wherein said first moulding element (4 a) and second moulding element (4 b) are configured for being superposed one on another at an open lateral surface so as to define a containing volume of said medical cement in a superposed configuration of said first element (4 a) and second element (4 b), and a passage hole (6) for enabling passage of a portion of said medical cement for realising said orthopaedic spacer for said specific patient.
 7. The mould (1) according to claim 1, further comprising a plurality of said first forming inserts (14), inter-replaceable and respective portions (8, 12) of the surface (3) which have a shape, width and/or length that are different so as to realise a forming of orthopaedic spacers having different shapes and/or dimensions.
 8. A method for forming an orthopaedic spacer comprising steps of: predisposing a mould (1) according to claim 1; providing said reinforcing element (15); choosing a first forming insert (14) from among a plurality of first forming inserts according to conformational and/or dimensional aspects of the desired spacer; providing said second forming insert (9); arranging said first forming insert (14) in said mould (1); arranging the second insert (9) in the mould; positioning the reinforcing element in the mould so that it is located in the first insert (14); inserting bone cement in said mould (1); pressing said mould (1); and once the bone cement has hardened, extracting the orthopaedic spacer from the mould. 